1. Field of the Invention
The present invention is directed to a surface resonator having two adjacently disposed windings of the type used in conducting examinations with nuclear magnetic resonance equipment.
1. Description of the Prior Art
A surface coil of the type suitable for use in nuclear magnetic resonance equipment having two adjacently disposed windings is described in the article "Counter-Rotating Current Local Coils for High Resolution Magnetic Resonance Imaging," in Magnetic Resonance in Medicine, Vol. 3, 1986 at pages 590-603. Two loop-gap resonators are disclosed therein which are disposed adjacent to each other, and electrically coupled to each other. Two resonance conditions having different resonant frequencies are possible, whereby the currents in the loop-gap resonators flow in the same direction in one case, and in opposite directions in the other case. Coupling of this surface resonator to the nuclear magnetic resonance equipment is undertaken with a coupling coil arranged in the inside of the surface resonator.
Surface resonators are used in the same manner as surface coils when signals from a locally limited examination region are to be acquired with increased resolution. Such surface resonators can also be used as a transmitter as well as a receiver for imaging and spectroscopy. In all applications, however, the coupling coil disposed inside the surface resonator prevents complete symmetry from being achieved, so that the respective transmission and reception fields lose homogeneity. Transformation losses are also associated with the inductive coupling. When such a resonator is used for imaging, image disturbances occur as a result of the presence of the coupling coil.